Ultra-low-profile tube-type magnetics

Abstract

A low-profile transformer or inductor includes a leg of a magnetically permeable core. A tube-type winding arrangement is made by use of a flat, flexible dielectric sheet, on one side of which a broad conductive area is affixed, and on the other side of which a plurality of mutually parallel elongated regions are affixed. The dielectric sheet is rolled into a tube defining a parting line which is perpendicular to the axes of elongation of the conductive strips. The discontinuous elongated strips are formed into a continuous winding by means of stitches. The stitches may be through vias extending through overlapping regions of the tube to interconnect ends of the strip conductors, or may be generated by an HDI conductor overlying the ends of the strip conductors, with through vias making connections to the ends of the strip conductors and to HDI conductors.

What is claimed is: 
     
       1. A magnetically coupled winding structure, comprising: a flat, magnetically permeable core including a flat first portion defining first and second broad sides and at least one peripheral edge, and also defining mutually parallel first and second slots extending inward from said edge, to thereby define a central core portion lying generally between said first and second slots, and to also define first and second side core portions extending parallel with said central core portion, said magnetically permeable core further including a flat, magnetically permeable end portion coplanar with said first portion and magnetically coupled to said central core and to said first and second side core portions adjacent the ends of said slots;   a dielectric sheet defining first and second broad, flat, mutually opposed sides, said dielectric sheet including a first electrically conductive layer affixed to at least a substantial portion of said first side, and further including a second layer affixed to said second side of said dielectric sheet, said second layer including a plurality of elongated second electrical conductors, each of said plurality of elongated second electrical conductors defining first and second ends, and an axis of elongation extending between said first and second ends, with said axes of elongation of said second electrical conductors being mutually parallel, said dielectric sheet being curved in a generally cylindrical manner to thereby define a structure having the general shape of a flat tube defining first and second ends and having said first side of said dielectric sheet on the inner side of said flat tube, said flat tube defining a central axis, and being dimensioned to fit over said central core portion with said first end of said tube adjacent the juncture of said central core portion and said side core portions, and with said second end of said tube adjacent said end portion of said core, so that said first electrically conductive layer is formed into an electrically open single turn about said central core, and so that each of said second electrical conductors also defines an open single turn about said central core, with a first end of each of said elongated second electrical conductors adjacent a second end thereof, said first and second ends of said second electrical conductors being substantially coplanar with one of said first and second broad sides of said magnetically permeable core when said tube is fitted over said central portion of said core;   a flexible interconnection sheet overlying said one of said first and second sides of said magnetically permeable core and said first and second ends of said second elongated electrical conductors, said flexible interconnection sheet including a layer of electrically conductive material defining at least interconnections between said first and second ends of said elongated second electrical conductors, said interconnections being defined in a manner which electrically interconnects at least the first end of one of said elongated second electrical conductors to the second end of a nearby one of said elongated second electrical conductors, to thereby define a single continuous electrical conductor wound in multiple turns about said central core portion; and   electrically conductive means coupled to mutually adjacent portions of said electrically conductive first layer, to thereby define a single turn of electrical conductor about said central core portion of said magnetically permeable core.   
     
     
       2. A magnetically coupled winding structure according to claim 1, wherein said interconnections of said interconnection sheet are defined in a manner which electrically interconnects at least the first end of one of said elongated second electrical conductors to the second end of an adjacent one of said elongated second electrical conductors, to thereby define a single continuous electrical conductor lying only on said second side of said dielectric sheet and on said interconnection sheet, and wound in multiple turns about said central core portion. 
     
     
       3. A structure according to claim 1, wherein said first electrically conductive layer affixed to at least a substantial portion of said first side of said dielectric sheet defines first and second projecting tabs, said projecting tabs of said first and second electrically conductive layer being such that, when said dielectric sheet forms said tube defining first and second ends, said projecting tabs are adjacent one of said first and second ends. 
     
     
       4. A structure according to claim 1, wherein said first electrically conductive layer affixed to at least a substantial portion of said first side of said dielectric sheet defines first and second projecting tabs, said projecting tabs of said first and second electrically conductive layer being such that, when said dielectric sheet forms said tube defining first and second ends, said projecting tabs are adjacent said first end of said tube. 
     
     
       5. A magnetically coupled winding structure, comprising: a flat, magnetically permeable core including a flat first portion defining first and second broad sides and at least one peripheral edge, and also defining at least a first slot extending inward from said edge, to thereby define a central core portion lying generally adjacent said first slot, and to also define at least a side core portion extending parallel with said central core portion, said magnetically permeable core further including a flat, magnetically permeable end portion coplanar with said first portion and magnetically coupled to said central core portion and to said first side core portion adjacent the end of said slot;   a dielectric sheet defining first and second broad, flat, mutually opposed sides, said dielectric sheet including a first electrically conductive layer affixed to at least a substantial portion of said first side, and further including a second layer affixed to said second side of said dielectric sheet, said second layer including a plurality of elongated second electrical conductors, each of said plurality of elongated second electrical conductors defining first and second ends, and an axis of elongation extending between said first and second ends, with said axes of elongation of said second electrical conductors being mutually parallel, said dielectric sheet being curved in a generally cylindrical manner to thereby define a structure having the general shape of a flat tube defining first and second ends and having said first side of said dielectric sheet on the inner side of said flat tube, said flat tube defining a central axis, and being dimensioned to fit over said central core portion with said first end of said tube adjacent the juncture of said first central core portion and said side core portion, and with said second end of said tube adjacent said end portion of said core, so that said first electrically conductive layer is formed into an electrically open single turn about said central core portion, and so that each of said second electrical conductors also defines an open single turn about said central core portion, with a first end of each of said elongated second electrical conductors adjacent a second end thereof, said first and second ends of said second electrical conductors being substantially coplanar with one of said first and second broad sides of said magnetically permeable core when said tube is fitted over said central portion of said core;   a flexible interconnection sheet overlying said one of said first and second sides of said magnetically permeable core and said first and second ends of said second elongated electrical conductors, said flexible interconnection sheet including a layer of electrically conductive material defining at least interconnections between said first and second ends of said elongated second electrical conductors, said interconnections being defined in a manner which electrically interconnects at least the first end of one of said elongated second electrical conductors to the second end of a nearby one of said elongated second electrical conductors, to thereby define a single continuous electrical conductor wound in multiple turns about said central core portion; and   electrically conductive means coupled to mutually adjacent portions of said electrically conductive first layer, to thereby define a single turn of electrical conductor about said first central core portion of said magnetically permeable core.   
     
     
       6. A structure according to claim 5, wherein said flat, magnetically permeable core further defines at least a second slot extending inward from said edge, parallel with said first slot, to thereby define second side portion lying generally adjacent said second slot, said second side portion lying parallel with said central core portion, and said flat, magnetically permeable end portion being coplanar with said central portion of said magnetically permeable core and with said first and second side portions of said magnetically permeable core. 
     
     
       7. A method for fabricating a magnetically coupled winding structure comprises the steps of: defining an electrically conductive primary winding conductor affixed to one broad side of a flat, flexible dielectric substrate;   defining a plurality of electrically conductive regions on the other broad side of said dielectric substrate, each of said regions being elongated in the direction of an axis of elongation, and said axes of elongation being parallel;   rolling said dielectric substrate into the general shape of a tube defining an interior aperture and a parting line, whereby said axes of said elongated regions are formed into curved figures, said tube having an axis which is orthogonal to the plane of said figures, said elongated regions being electrically discontinuous along said parting line;   causing said aperture of said tube to surround a leg of a magnetically permeable core;   stitching together mutually adjacent ends of said elongated regions by creating through vias which interconnect ends of said elongated regions in a manner which forms at least some of said elongated regions into a continuous turn of winding about said leg.   
     
     
       8. A method according to claim 7, wherein said step of causing said aperture to surround said leg includes the step of forming said dielectric substrate with said electrical conductors around said core. 
     
     
       9. A method according to claim 7, wherein said step of causing said aperture to surround said leg includes the step of forming said dielectric substrate with said electrical conductors into a tube-like form in the absence of said magnetically permeable core. 
     
     
       10. A method according to claim 9, wherein said step of forming said dielectric substrate includes the step of forming said dielectric substrate over a mandrel having dimensions similar to those of said leg of said magnetically permeable core. 
     
     
       11. A method according to claim 7, wherein said step of stitching includes the step of juxtaposing a second dielectric substrate over at least a portion of said parting line, said second dielectric substrate including at least a second conductive region, and creating each stitch by creating a first through via in contact with an end of one of said elongated regions and with said second conductive region, and a second through via in contact with an end of another one of said elongated regions and with said second conductive region.